Mathematics from zero
Exponents
To write “2 added to itself” you use 2 + 2. To write “2 multiplied by itself five
times” you would need 2 × 2 × 2 × 2 × 2. That is long. Mathematics has a shorthand
for it — and that shorthand is the exponent.
After this lesson you can say what an exponent means, name its two parts, work out a small power by multiplying, explain what raising to the power 1 and 0 do, and describe why exponents make numbers grow so fast.
An exponent is repeated multiplication, written short. Just as multiplication is
repeated addition, raising to a power is repeated multiplication. We write it with a
small raised number: 2⁵ means 2 × 2 × 2 × 2 × 2. The big number is multiplied by
itself, and the small one counts how many times it appears.
The two parts are the base and the exponent. In 2⁵, the 2 is the base — the
number being multiplied — and the 5 is the exponent — how many copies of the
base are multiplied together. We read 2⁵ as “2 to the power 5”. Two special powers
have names of their own: n² is “n squared”, n³ is “n cubed”.
Raising to the power 1 leaves the number alone; raising to the power 0 gives 1. 7¹
is just one copy of 7, so 7¹ = 7. And 7⁰ = 1 — for every base. Watch the pattern
going down: 2³ = 8, 2² = 4, 2¹ = 2. Each step down divides by the base. One more
step down: 2⁰ = 2 ÷ 2 = 1. The pattern forces it.
Exponents make numbers grow startlingly fast. The curve above is 2 raised to each
power from 0 to 6. It barely lifts off, then shoots upward: 2¹⁰ is already 1024.
Multiplication adds the same amount each step; exponents multiply by the base each
step, so the total runs away. This explosive growth is why exponents matter far beyond
arithmetic.
Work out 3⁴.
The base is 3, the exponent is 4 — so multiply four 3s together: 3 × 3 × 3 × 3.
Take it two at a time. 3 × 3 = 9. Then 9 × 3 = 27. Then 27 × 3 = 81.
So 3⁴ = 81. Notice how fast it climbed: 3¹ = 3, 3² = 9, 3³ = 27, 3⁴ = 81 —
each step multiplied the result by 3 again.
Why this works
Why does anything to the power 0 equal 1, not 0? Follow the staircase down. 2³ = 8,
2² = 4, 2¹ = 2 — every step down divides by 2. To keep the pattern unbroken, the
next step must be 2 ÷ 2 = 1. Defining 2⁰ = 1 is the only choice that keeps the
rule “step down, divide by the base” working all the way.
Common mistake
The most common mistake is reading 2³ as 2 × 3 = 6. The exponent is not a factor —
it is a count of factors. 2³ is 2 × 2 × 2 = 8. Always ask: how many copies of the
base? Then multiply that many of them together — never multiply the base by the
exponent.
Work out 2³ (that is 2 × 2 × 2). Type the value.
Work out 5² (5 squared). Type the value.
Work out 7⁰. Type the value.
Work out 4¹. Type the value.
Work out 2⁵ (2 × 2 × 2 × 2 × 2). Type the value.
What does 3² mean?
An exponent is shorthand for repeated multiplication: 2⁵ means five 2s multiplied
together. The base is the number being multiplied; the exponent counts how many copies.
Raising to the power 1 leaves a number unchanged; raising to the power 0 gives 1, to
keep the step-down pattern unbroken. Because each step multiplies by the base again,
exponents make numbers grow far faster than multiplication ever does.